FIG. 1 shows the structure of an existing ultrasonic transducer, which mainly comprises a piezoelectric layer 101, a matching layer 102, a backing layer 103, and an acoustic lens 104 (or acoustic delay line), when an electrical signal is applied across the piezoelectric layer 101, the piezoelectric vibrator will vibrate and radiate acoustic signal forward and backward respectively, the forward acoustic signal passes through the matching layer 102 and the acoustic lens 104 (or acoustic delay line) with a certain degree of attenuation, then it enters the object to be detected; and the backward acoustic signal is mostly attenuated and absorbed by the backing layer 103, being wasted in the form of heat, therefore the backward acoustic wave is not utilized effectively. In this type of ultrasonic transducer, the sound energy reflection coefficient R of the interface between the piezoelectric layer 101 and backing layer 103 is:
            R      2        =                  (                                            Z              p                        -                          Z              b                                                          Z              p                        +                          Z              b                                      )            2        ,
wherein Zp is the acoustic impedance of the piezoelectric layer, and Zb is the acoustic impedance of the backing layer.
FIG. 2 shows the time domain and frequency domain characteristics simulated by a conventional ultrasonic transducer structure.
China patent application (Application No. 201210339333.8) provides a technical solution including a dematching layer with relative high acoustic impedance arranged at the back of a wafer, wherein the dematching layer has an acoustic impedance in the range of from 40 MRayls to 120 MRayls, so as to increase the energy of the forward ultrasound, and improve the performance of the ultrasonic transducer, but the dematching layers of higher acoustic impedance are mostly made of metallic materials which are not easy to cut in the array ultrasonic probe process, as a result they may damage the blade employed in the array cutting process. With respect to adding a dematching layer of higher acoustic impedance on the rear surface of a wafer as a hard surface for reflecting most of the sound wave, the corresponding wafer has the thickness of ¼ wavelength, which is ½ thinner than the thickness of the wafer in the structure comprising soft surface of common backing material, wherein the later wafer has the thickness of ½ wavelength, both structures using the same working frequency probe, and the probe employing a dematching layer requires much thinner wafer, which increases the difficulty of the process.
China patent application (Application No.: 201310002007.2) provides a technical solution including a plurality of back efficiency layers with different acoustic impedance values are arranged at the back of a wafer, the number of back efficiency layers employed in this invention is too much, and the acoustic impedance values of the back efficiency layers become smaller one by one, which increases the complexity and instability of the process to a certain degree, so it is difficult to manufacture.